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latencytop: fix kernel panic while reading latency proc file 

Reading /proc/<pid>/latency or /proc/<pid>/task/<tid>/latency could cause
NULL pointer dereference.

In lstats_open(), get_proc_task() can return NULL, in which case the kernel
will oops at lstats_show_proc() because m->private is NULL.

When get_proc_task() returns NULL, the kernel should return -ENOENT.

This can be reproduced by the following script.
while :
do
        date
        bash -c 'ls > ls.$$' &
        pid=$!
        cat /proc/$pid/latency &
        cat /proc/$pid/latency &
        cat /proc/$pid/latency &
        cat /proc/$pid/latency
done

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Hiroshi Shimamoto 2008-02-14 10:26:24 -08:00 committed by Ingo Molnar
parent 2d07b255c7
commit ae0027869d
1 changed files with 2 additions and 0 deletions
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2
fs/proc/base.c
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@ -350,6 +350,8 @@ static int lstats_open(struct inode *inode, struct file *file)
struct seq_file *m;
struct task_struct *task = get_proc_task(inode);
if (!task)
return -ENOENT;
ret = single_open(file, lstats_show_proc, NULL);
if (!ret) {
m = file->private_data;